The present invention relates to a method of laterally joining product wrappings.
The present invention is particularly suitable for wrapping substantially parallelepiped products, such as single or groups of cigarette packets to which the following description refers purely by way of example.
Such products are normally wrapped by first forming a tubular wrapping about the product, usually by means of a wrapping device comprising a wrapping wheel with a number of peripheral radial seats, each designed to receive a sheet of wrapping material and a respective product at a loading station.
As the sheet is fed inside the seat, it is folded in a U about the product so as to present two projecting longitudinal portions, which are folded one on top of the other to define an overlapping lateral portion, and then connected to define said tubular wrapping.
Each product complete with the tubular wrapping is then unloaded off the wrapping wheel at an unloading station by means of a transfer device normally comprising a gripping and/or control element for engaging the overlapping lateral portion of the wrapping.
The two overlapping sheet portions are normally gummed together or heat-sealed in the case of heat-sealable wrapping material.
The above known wrapping method presents several drawbacks due to the manner in which the two overlapping sheet portions are joined.
In the case of a gummed joint, the wrapped products may, under certain operating conditions, reach the unloading station before the gum is dry, thus resulting in the wrapping coming unstuck and the product automatically being rejected.
In the case of heat-sealing, on the other hand, the design of the wrapping device as described above is enormously complicated by the presence of heat-sealing devices on the wrapping wheel or along the path of the products between the loading and unloading stations.